Ecology of the thessalhydra and thessalmonsters

In a previous post I introduced the Hydra into my campaign setting as the singular monster from Greek mythology and explained the generic hydra monsters as being its severed members. This is due both to my respect for the original myth and my disbelief that any ecosystem could support hydras. Here I include my take on the thessalmonster family...

Although the hydra is a unique dragon that haunts the swamps of Lerna, its severed heads have given rise to the hydras that terrorize the world beyond its territory. Although their essential nature as a perpetually diluting bloodline remains constant, along the way the hydras have undergone various mutations such as the cryohydra, electrohydra, hydralisk, pyrohydra and schism hydra. One such mutation is the thessalhydra, which has itself given rise to the thessalmonsters.

Sexual cannibalism as reproduction

An idea I got the other day was that some monsters could reproduce by sexual cannibalism. Not simply eat their partner during or after sex, but eat their partner in order to inseminate their eggs.

According to the quasi-canon Dune Encyclopedia, the male sand-worm consumes the female, inseminates her eggs inside his body, then lays the egg case himself. The female does not survive the process, but she does not need to.

According to a suggestion by Derek Holland, the thessalmonster could reproduce by "hemiclone." Every thessalmonster is an asexual female who fertilizes her eggs by eating another monster. The offspring will be a hybrid of thessalhydra and whatever the "father" was, leading to the many varieties like thessalgorgon, thessalisk, thessalmera, thessalnaga, thessaltrice, etc. Every thessalmonster only passes on the traits of the thessalhydra to her offspring, so the traits of past "fathers" are not inherited by subsequent generations.

Ecology of the (Lernaean) Hydra

In mythology, the hydra was a unique monster that terrorized Lerna. In fantasy gaming the hydra has been expanded into an entire species, one that is typically depicted as a naturally occurring animal with a place in the local ecology (which I find highly questionable). I was elated to discover that Rolang proposed a compromise between the two views: every hydra grew from the severed head of another hydra, going back to the original Hydra still living on Lerna.